There is a significant clinical need for hard and soft tissue grafting for the reconstruction of musculoskeletal damage due to trauma, chronic disease and congenital anomalies. Bone and/or cartilage grafts are often used to assist in the repair or healing of musculoskeletal damage. Such grafts of natural tissues, such as cortical or cancellous bone, can be autografts, allografts or xenografts. Autografts are “self” grafts of bone and/or cartilage taken from a donor site in the patient and transplanted to the host site of the same patient. Allografts are grafts transplanted from a donor of the same species as the intended recipient, but are not autografts, i.e., the graft comes from another patient or a cadaver. Xenografts are grafts taken from a different species from the intended recipient.
Autografts harvested from the patient at the time of surgery are the standard for grafting. Autografts have been shown to promote bone growth at the site of grafting (osteoinductive), form new bone themselves (osteogenic) and provide a scaffold for bone ingrowth (osteoconductive). Advantageously, as autografts are harvested from the same patient in which they are to be transplanted, there is little or no risk of “rejection” of the graft or of transmitting viruses. Unfortunately, a patient has a limited supply of donor bone for grafting. Additionally, autografts can often suffer from donor site morbidity.
Allografts and xenografts are available in greater supply than autografts. However, they are less osteoinductive, they may induce a greater immunogenic response (e.g., inflammation, graft rejection, etc.) and they suffer from a higher risk of disease transfer compared to autografts. As a result, adjunct therapies are often used with allografts and xenografts to augment and/promote bone regeneration and repair.
Adjunct therapies include the use of biomaterials that promote cellular infiltration and osteogenesis and biologics such as bone morphogenetic proteins (BMPs), which stimulate cell replication and activity. While these adjuvant therapies increase graft remodeling and new bone formation, they are costly and include risk factors such as osteosarcoma, marrow fibrosis and ectopic bone formation. The use of allografts and xenografts to augment bone healing is expensive and the failure rate is relatively high.
Alternative, musculoskeletal graft substitutes continue to be researched. The ideal material for musculoskeletal regeneration is a biomaterial that is biocompatible, capable of supporting biological integration and full restoration of native tissue, and is preferably biodegradable. Furthermore, it is preferred that bone graft substitutes favorably interact with a variety of host cells involved in tissue regeneration and integration. However, despite the extensive research in this field, synthetic bone graft substitutes often fail to meet all of these criteria. Thus, there is a need to provide a biocompatible material that can be used as a musculoskeletal graft substitute having the properties suitable for musculoskeletal repair and regeneration, and methods for making such materials.